Asquare metal plate 1.5m side and 1.2mm thick weighting 50n is to be lifted through a vertical gap at 25mm of infinite extent . the oil in air gap has a specific gravity of 95 percent and viscosity of 2.5n. s/m^2. if the metal plate is to be lifted at a constant speed of 0.1m/s find the force and power required.

Viscous force on the plate is given by

Buoyancy force on the plate is given as

Weight of the plate = 50 N

Now for constant speed of plate the net force on it must be zero

SO here we can say

So it will require a constant force of 493.6 N

correct it is c.) b b

there is no correct list among the choices you've provided.

the list might look something like this:

-- baby human

-- piccolo

-- flute

-- soprano singer

-- trumpet

-- tenor singer

-- trombone

-- baritone singer

-- baritone horn

-- bass singer

-- tuba

since i had to make up the list myself, i made it easy on myself, and i didn't try to shuffle the string instruments and woodwinds into it too.